U.S. Pat. Nos. 4,854,984 and 4,919,738 disclose a bonding apparatus for bonding portions of plural workpiece layers together, wherein at least one of the workpiece layers comprises a thermoplastic layer. The apparatus comprises a patterned cylinder 22, an anvil cylinder 24, and means 26 for adjustably biasing the cylinders 22 and 24 together. The patterned cylinder 22 is provided with a xe2x80x9csaw-tooth shape pattern of protuberances 51 which extend circumferentially about each end of the cylinder,xe2x80x9d see column 4, lines 65-67 of the ""984 patent. The biasing means 26 comprises pressure regulating means 55 and a pneumatic actuator means 56. The pressure regulating means 55 is coupled to a supply source P of pressurized air and to the pneumatic actuator means 56 and controls the pressure applied by the pneumatic actuator means 56 to the cylinders 22 and 24. Neither the ""984 patent nor the ""738 patent discloses means for adjustably forming discrete lengths of bonded portions within the workpiece layers.
It is also known to bond portions of plural workpiece layers using an apparatus similar to the one disclosed in the ""984 patent where, in place of a patterned cylinder, a support roll, a mounting ring coupled to the support roll and a patterned tool coupled to the mounting ring, are provided. Cams are also provided on the support roll. They engage an anvil cylinder and define when the patterned tool and anvil cylinder come together so as to apply sufficient compressive forces to workpiece layers passing therebetween to bond desired, discrete portions of the workpiece layers. For example, plural workpiece layers may include a plurality of sequential workpiece sections, wherein each workpiece section is bonded to include at least one bonded portion. Further, center points on sequential workpiece sections are separated from one another by a predefined pitch. In order to vary one or more of the length of a bonded portion and the workpiece section pitch, modified cams and a modified patterned tool are typically provided.
Accordingly, there is a need for a bonding apparatus, wherein the lengths of the bonded portions and workpiece section pitch can be varied without requiring the installation of modified tooling and cams.
An apparatus is provided for dynamically bonding plural workpiece layers together. The apparatus comprises: a first assembly including a rotatable element having an outer circumferential portion adapted to engage one of the workpiece layers; a second assembly including an anvil roll adapted to engage another of the workpiece layers and defining with the rotatable element a nip for receiving the workpiece layers; a drive mechanism for effecting rotation of the rotatable element and the anvil roll; servo motor apparatus for applying a predefined force to at least one of the rotatable element and the anvil roll so as to bias the rotatable element and the anvil roll together; and a control system coupled to the servo motor apparatus for varying the force applied by the servo motor to the at least one of the rotatable element and the anvil roll such that the outer circumferential portion of the rotatable element and the anvil roll engage and bond together predefined portions of the plural workpiece layers passing through the nip.